Statistical analyses
Statistical analyses were performed
with SPSS 22.0 (IBM, Armonk, USA). Quantitative variables were presented
as means ± standard deviations and categorical variables were expressed
as frequencies and percentages. The data were analyzed using the
Chi-squared test, one-way analysis of variance (ANOVA) or Bonferroni
test as appropriate. Logistic regression analysis was performed to
explore the effects of post-thawed culture period on live birth after
controlling for potential confounders including female age, female BMI,
endometrial preparation, type of infertility and duration of
infertility. A two-sided P -value < 0.05 was considered
to be statistically significant.